package collection;

import java.util.Collection;
import java.util.HashSet;

public class CollectionDemo1 {
    public static void main(String[] args) {
        Collection c = new HashSet<>();
        c.add("one");
        c.add("one");
        c.add("two");
        c.add("three");
        c.add("four");
        c.add("five");
        System.out.println(c);
        int size = c.size();
        System.out.println(size);
        boolean isEmpty =c.isEmpty();
        System.out.println("是否为空集："+isEmpty);

    }
}
